Summation formulae in the theory of thin films

On the basis of general summation formulae for light reflected and transmitted by a thin film the author derives formulae for a thin dielectric film, for a thin metallic film and for a system of thin dielectric films. This solution is based on Stokes's principle of reversibility, which is the idea unifying the cases into one theory. In conclusion he gives the solution of a general case, dealing with light reflected and transmitted by a system of thin dielectric and metallic films.

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The application of the thermodynamics of irreversible processes to welding arcs

The self-regulation of an inert gas shielded metal welding arc is dealt with briefly. A thermodynamic equation is derived for the self-regulation of such an arc.

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Experimentelle Untersuchungen über das Verteilungsgesetz der Ferromagnetischen Bereiche nach dem Kriterium der Koerzitivkraft

Zusammenfassung Aus Messungen der inneren Reibung in magnetischen Feldern, die durch das Überlagern eines magnetischen Wechselfeldes über ein magnetisches Gleichfeld zustande gekommen sind, werden Schlußfolgerungen gezogen über die Art, wie sich die Verteilung der ferromagnetischen Bereiche nach dem Standpunkt der Koerzitivkraft im Magnetisierungsprozeß in einem magnetischen Gleichfeld verändert. Aus Messungen der inneren Reibung in magnetischen Wechselfeldern mit gleicher Amplitude aber verschiedenen Frequenzen wird die Schlußfolgerung gezogen, daß die Wände jener Bereiche, welche verschiedene Koerzitivkräfte haben, erzwungene Schwingungen mit verschiedener Geschwindigkeit aufweisen.

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Zur Labyrinthstruktur bei Martensit

Ohne Zusammenfassung

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Change in primary extinction during decomposition of supersaturated solid solution

The integrated intensity of the matrix reflection (200) was measured during the precipitation of the, and phases. The observed effects were explained as the consequence of lattice defects formed in the neighbourhood of precipitate particles.

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(200) , . .

     

A contribution to direct processes in the Co59(p,n) reaction forE p ∼ 6·5 MeV

Nuclear emulsions were used to study the energy spectrum and forward-backward asymmetry of neutrons from the Co⁵⁹(p,n) reaction forE _p 6·5 MeV. It was found that the decay of the compound nucleus makes a maximum contribution of 50% to the reaction yield. Energies of some excited states of the Ni⁵⁹ nucleus were also determined.

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Co⁵⁹(p,n) E _p 6,5 MeV

- Co⁵⁹(p,n) E _p 6,5 MeV. , 50%. , Ni⁵⁹.

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The authors would like to thank all those who helped in this work, particularly all members of the cyclotron group of the Nuclear Research Institute of the Czechoslovak Academy of Sciences, who so willingly helped with the irradiation, and H. Koutová from the Faculty of Technical and Nuclear Physics, who carefully measured the emulsions. Our thanks are also due to R. Krejová from the Faculty of Technical and Nuclear Physics for developing the emulsions and J. Kopecký from the Nuclear Research Institute for providing the cobalt target.     

Choice of parameters of an X-ray monochromating unit

In recent papers a way of computing the monochromated wavelength distribution in some current experimental arrangements was presented. In this paper an application is shown for the Johansson monochromating unit. The conditions are indicated for attaining the desired breadth of the monochromated interval and for its maximum intensity. The analysis implies that it is not advantageous to use very narrow foci and that the crystals should be neither very perfect nor very imperfect. The optimum conditions must be found in each case separately.

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Determination of accuracy in measuring the parameters of tetragonal and hexagonal lattices

The procedure for determining the accuracy when measuring the parameters of tetragonal and hexagonal lattices is described. The accuracy can easily be calculated for all common methods by means of graphically represented functions. The relations derived can be used as quantitative criteria for the suitability of the combination of lines from which the lattice parameters are to be determined.

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New derivation of Bardeen-Shockley formula for mobility of electrons in homopolar semi-conductors

The Bardeen-Shockley formula for the mobility of an electron or hole in a homopolar semi-conductor is derived in a different way to that in which its authors obtained it. The interaction energy of the electron with the acoustic lattice oscillations is derived in an original way. A new possibility for determining the energy gap is given.

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Fundamental concepts of the theory of dislocations

The fundamental concepts of the theory of dislocations are given in an exact way and some theorems are proved.

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In conclusion the author would like to thank Professor M. Valouch and Professor L. Zachoval for the interest they took in this work and for remarks and advice which helped to improve it.     

On the mechanism of rendering visible dislocations on the surface of iron crystals by anodic dissolving

The paper contains further results of studying dislocations rendered visible by anodic dissolving on the surface of single crystals of alpha-iron. The influence of the crystallographic orientation of the surface is investigated, the effect of carbon is confirmed and the anodic process is studied. The mechanism of dissolving of the crystal is given and a new more suitable method of rendering dislocations visible is derived.

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The author thanks F. Kroupa and J. Hejduk for critical remarks and discussion.     

Der Exzitonenzerfall im elektrostatischen Felde der Störstellen von Ionenkristallen

Zusammenfassung Es wird theoretisch der Prozeß des Exzitonenzerfalls mit Hilfe der Ionisation durch das elektrostatische Feld der Störstelle untersucht. Die Wirkungsquerschnitte werden in zwei Grenzfällen bestimmt: bei einer kleinen und einer großen mittleren freien Bahn des Exzitons, die durch dessen Wechselwirkung mit den Phononen bedingt ist. Die Ergebnisse werden zum Studium des Exzitonenzerfalls an einer Vakanz nach einem Kupferion in Cu₂O-Kristallen mit einem stöchiometrischen Sauerstoffüberschuß verwendet.

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The connection between low-gradient form of the positive column in oxygen and moving striations

The method of sliding photomultipliers was used to study the connection between two forms of the positive column in oxygen — the so-called low-gradientT-form and the highgradientH-form — and the presence of moving striations in the positive column. It was shown that in theT-form of a positive column striations are always present which move from the cathode to anode with a velocity of several thousand metres/sec. The highgradient form of theH-positive column, on the other hand, is not striated. The non-single-valuedness of the value of the longitudinal electric field in a discharge in oxygen is thus explained by the presence or absence of phenomena of a time variable character.

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Studium der photodielektrischen Erscheinung an lumineszierenden Zinkkadmiumsulfiden

Zusammenfassung Die spektrale Abhägigkeit der photodielektrischen Eigenschaften der lumineszierenden Zinkkadmiumsulfide verschiedener Zusammensetzung zeigt, da eine Beimengung von Kupfer das Eintreten von Zuständen mit groer Polarisierbarkeit hervorruft, die eine Änderung der realen Komponente der Dielektrizitätskonstanten zur Folge haben. Die Kupferkonzentration kann dabei so gering sein, da sie in der Lumineszenzemission gar nicht zur Geltung kommt. Die Infrarotmaxima der Verluste entsprechen Niveaus, die von anderen Autoren und mit anderen Methoden festgestellt wurden. Das Maximum des Exzitationsspektrums im Bereiche des Ausläufers der Absorptionskante hängt mit dem Maximum der Änderung der realen Komponente der Dielektrizitätskonstante zusammen.

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Nunmehr im Physikalischen Institut der Karlsuniversität, Prag.     

The change in primary extinction during decomposition of a super saturated solid solution 1. System Al-Ag

On the basis of the correlation of diffraction data (intensity and width) of a precipitate with the intensity of reflection of a matrix solid solution it is shown that the change in primary extinction during the decomposition of a solid solution of Agin Alis caused by the precipitation of the phase Ag₂Aland not by the production of lattice defects (zones, stacking faults).

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I. Al-Ag

( ) , Ag Al Ag₂Al, ( , ).

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Reported in part at the VIth Scientific Technical Conference on the Application of X-rays held in Leningrad in 1958.

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The author thanks M. Mikovský for preparing the single crystals of the alloy Al-Ag having a high primary extinction and J. Laek and Prof. J. Bedná for carefully checking their homogeneity and chemical composition.     

Wavelength distribution of X-rays in the focus of a monochromator and an estimate of the influence of this distribution on precision measurements of lattice constants

Wavelength distribution in the focus of a Johansson type monochromator is computed assuming the tube focus emissivityG(), reflection curveR() and wavelength distribution of the incident radiationJ(-₀) are known. It is shown e.g. that the centre of gravity may be shifted in accordance with the position of the crystal on the focal circle which may considerably influence precision measurements of lattice parameters.

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, G(,) R() J(-₀) . , , , .

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The author is grateful to Z. Hemanová for carrying out all the computations very carefully.     

On the electroluminescence of powdered zinc sulphide layers

The experimental study of the dependence of the electroluminescence brightness on the voltage confirms the correctness of the mechanism of electroluminescence, based on impact ionization in parts of the crystal where the electric field is concentrated. A study of the photoluminescent and electroluminescent spectra of phosphors containing two activators (copper and an element of rare earth) permits the determination of the magnitude of the volume of the crystal in which electroluminescence occurs. A study of the influence of the stored light sum on the brightness of electroluminescence and a study of the rate of growth of the variable and constant components of electroluminescence point to the fact that the excitation is transferred from the region of field concentration to the whole volume of the crystal.

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The effect of the orientation of zinc single crystals and of the rate of growth on the direction of cell substructure

The effect of the orientation of zinc single crystals and the rate of growth on the direction of the formation of cellular substructure is observed. A model accounting for the observed dependences is proposed.

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A study of the influence of dislocations on some of the magnetic properties of permalloy alloys

The influence of dislocations produced during plastic pulling on some magnetic properties is studied experimentally with special attention to the coercive force of Fe-Ni alloys with a cubic face-centred lattice. Vicena's theory of the influence of dislocations on the coercive force is rendered more accurate and the dependences of the coercive force on the plastic lengthening of the samples are derived for the above-mentioned alloys; the results are compared with the measured dependences. The observed anomalies are explained.

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In conclusion the author would like to thank J. Kaczér for many suggestions and advice, F. Kroupa for advice and cooperation in the theoretical part of the paper and particularly J. Grolmus for carefully carrying out the many measurements and for all-round help in the experimental work. He also thanks V. Kamberský for carrying out some of the measurements and finally V. Janovec for some remarks and for carefully reading the paper.     

Spectral composition of thermoluminescence of coloured NaCl crystals

The paper gives the experimental results of studying the spectral composition of thermoluminescence in the different maxima in photo-chemically coloured pure NaCl crystals or NaCl-crystals containing Cu in different concentrations.

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NaCl

NaCl .